Dataset: GP15 pH Leg 1
Deployment: RR1814

Water column fish and bottle pH data

Principal Investigator:

Gregory A. Cutter (Old Dominion University, ODU)

Co-Principal Investigator:

Nicole R. Buckley (Old Dominion University, ODU)

Contact:

Gregory A. Cutter (Old Dominion University, ODU)

BCO-DMO Data Manager:

Shannon Rauch (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Project:

US GEOTRACES Pacific Meridional Transect (GP15) (U.S. GEOTRACES PMT)

US GEOTRACES PMT: hydrogen sulfide as a strong ligand affecting trace metal cycling (PMT Hydrogen Sulfide)

Deployment Synonyms:

GP15, GP15 Leg1, 33RR20180918, PMT, US GEOTRACES PMT

Data URL:

https://osprey.bco-dmo.org/dataset-deployment/838182/data

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Description

Methods & Sampling

Dataset acquisition description

Methodology:
60 mL of unfiltered water was subsampled from 12L GO-Flo bottles on the GTC carousel for each pH measurement. They were analyzed at sea in primarily single analyses using an automated Ocean Optics UV-VIS spectrophotometric system that was modified from Carter et al. (2013) with pure m-cresol purple (mCP) indicator dye. They were usually analyzed within 3 hours of collection and the salinity and temperature dependent pH equation from Clayton and Byrne (1993) was applied.

Sampling and analytical procedures:
Sampling followed the GEOTRACES cookbook sampling method. 60 mL of unfiltered water was subsampled from 12L GO-Flo bottles, mounted on the GTC carousel. The 60 mL polypropylene syringes were fitted with polycarbonate 3-way valves to remove air bubbles and prevent exchange of CO2 prior to analysis and rinsed 3 times with unfiltered water. The sample syringes were then kept at room temperature in the dark until placed in a circulating water bath at 25°C for a minimum of 20 minutes to bring the samples close to analysis temperature.

Once at analysis temperature, each syringe was attached to one of the ports on the automated syringe pump that delivered sample and dye to a 10 cm cell with an inner volume of 10 mL for sample seawater. The cell is placed in a thermostated-holder that is temperature controlled by water continuously pumped from a circulating water temperature bath, so the sample remains at 25±0.1°C during analysis. The samples were analyzed at sea within 3 hours of collection and the automated measurement sequence was initiated in LabVIEW and required a total processing time of 5 minutes.

Instruments:
The temperature of the absorbance cell is controlled using deionized water pumped from a VWR circulating water bath (Cat. No. 89202-966) and through the water-jacketed CUV-10 cuvette holder with a 10 cm pathlength, 10 mL volume cuvette with quartz windows. QP400-1-UV-VIS premium fiber optic cables are used from the HL-2000-FHSA light source to the CUV UV 10 cm cuvette holder and then to the Optics STS-VIS-L-25-400-SMA miniature spectrophotometer. The automation and data processing are controlled from a computer program written in LabVIEW. A Norgren Kloehn Versa Pump 6 syringe pump with a 4-way valve and 48000 step resolution was controlled by the LabVIEW program that delivers the sample, then dye to the cuvette.

Data Processing Description

Dataset Processing Description

Data processing:
LabVIEW (version 16.0) was used to automate the syringe pump and read the R value obtained from the spectrophotometer and approximate pH value prior to corrections. Salinity corrections were later applied using corresponding GEOTRACES bottle data. Dye corrections were later applied using the method of Clayton and Byrne (1993) using intercalibration samples provided by Andrew Dickson's lab at UCSD.

Two reference materials (B162 and B164) from Andrew Dickson's lab at UCSD were used to evaluate the uncertainty of our pH results collected at sea. pH values of 7.9143±0.0065 and 7.5532±0.0030 were recorded, in comparison the reported values for these reference materials were 7.9100±0.0005 and 7.5407±0.0010, respectively (Bockman and Dickson, unpublished). This translates to a 99.95% agreement for B162 and a 99.83% agreement for B164.

Known Problems:
For all of Station 27 and half of Station 29, the pH measurements are not trustworthy due to an error with the light source resulting in greater fluctuations of the λ434 absorbance reading (data are flagged 4). The integration time was increased, and the attenuator adjusted to fix this problem.

Quality Flags:
The SeaDataNet scheme was used to assign data quality flags to samples. More information can be found at https://www.seadatanet.org/Standards/Data-Quality-Control.
The reported codes for flagged data are:
0 = no quality control;
1 = good value;
2 = probably good value;
3 = probably bad value;
4 = bad value;
5 = changed value;
6 = value below detection;
7 = value in excess;
8 = interpolated value;
9 = missing value.

For intercalibration procedures, refer to the dataset's GEOTRACES Intercalibration Report (PDF).

BCO-DMO Processing:
- modified parameter names;
- added date/time fields in ISO8601 format.
Version history:
2021-05-06 (v2; current) - version 2 processed & published; includes corrections to event and sample numbers.
2021-01-26 (v1) - version 1 processed & published.

More information about this dataset deployment

Funding

Award Number	Funding Source
OCE-1737342	NSF Division of Ocean Sciences

Instruments

GeoFish Towed near-Surface Sampler

Supplied Name:

Supplied Description:

Instrument Type

Generic Name: GeoFish Towed near-Surface Sampler

Acronym: GeoFish

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/31/

Generic Description:

The GeoFish towed sampler is a custom designed near surface (<2m) sampling system for the collection of trace metal clean seawater. It consists of a PVC encapsulated lead weighted torpedo and separate PVC depressor vane supporting the intake utilizing all PFA Teflon tubing connected to a deck mounted, air-driven, PFA Teflon dual-diaphragm pump which provides trace-metal clean seawater at up to 3.7L/min. The GeoFish is towed at up to 13kts off to the side of the vessel outside of the ship's wake to avoid possible contamination from the ship's hull. It was developed by Geoffrey Smith and Ken Bruland (University of California, Santa Cruz).

GO-FLO Bottle

Supplied Name:

Supplied Description:

Instrument Type

Generic Name: GO-FLO Bottle

Acronym: GO-FLO

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/30/

Generic Description:

GO-FLO bottle cast used to collect water samples for pigment, nutrient, plankton, etc. The GO-FLO sampling bottle is specially designed to avoid sample contamination at the surface, internal spring contamination, loss of sample on deck (internal seals), and exchange of water from different depths.

Spectrophotometer

Supplied Name: automated Ocean Optics UV-VIS spectrophotometric system

Supplied Description:

Instrument Type

Generic Name: Spectrophotometer

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB20/

Generic Description:

An instrument used to measure the relative absorption of electromagnetic radiation of different wavelengths in the near infra-red, visible and ultraviolet wavebands by samples.

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
Station_ID	Station number	unitless	station
Start_Date_UTC	Date (UTC) at start of sample collection; format: DD/MM/YYYY	unitless	date
Start_Time_UTC	Time (UTC) at start of sample collection; format: hh:mm	unitless	time
Start_ISO_DateTime_UTC	Date and time (UTC) at start of sample collection; formatted to ISO8601 standard: YYYY-MM-DDThh:mmZ	unitless	ISO_DateTime_UTC
End_Date_UTC	Date (UTC) at end of sample collection; format: DD/MM/YYYY	unitless	date
End_Time_UTC	Time (UTC) at end of sample collection; format: hh:mm	unitless	time
End_ISO_DateTime_UTC	Date and time (UTC) at end of sample collection; formatted to ISO8601 standard: YYYY-MM-DDThh:mmZ	unitless	ISO_DateTime_UTC
Start_Latitude	Latitude at start of sample collection	degrees North	lat
Start_Longitude	Longitude at start of sample collection	degrees East	lon
End_Latitude	Latitude at end of sample collection	degrees North	lat
End_Longitude	Longitude at end of sample collection	degrees East	lon
Event_ID	Event number	unitless	event
Sample_ID	GEOTRACES sample number	unitless	sample
Sample_Depth	Sample depth	meters (m)	depth
PH_TOT_BOTTLE_gr5eba	pH, referred to total scale from bottle samples	unitless	pH
SD1_PH_TOT_BOTTLE_gr5eba	One standard deviation of PH_TOT_BOTTLE_gr5eba	unitless	pH
Flag_PH_TOT_BOTTLE_gr5eba	Quality flag for PH_TOT_BOTTLE_gr5eba	unitless	q_flag
PH_TOT_FISH_8srxc6	pH, referred to total scale from GeoFish samples	unitless	pH
SD1_PH_TOT_FISH_8srxc6	One standard deviation of PH_TOT_FISH_8srxc6	unitless	pH
Flag_PH_TOT_FISH_8srxc6	Quality flag for PH_TOT_FISH_8srxc6	unitless	q_flag

Database

Contribute Data

Dataset: GP15 pH Leg 1
Deployment: RR1814

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: GP15 pH Leg 1Deployment: RR1814

Dataset acquisition description

Dataset Processing Description

Dataset: GP15 pH Leg 1
Deployment: RR1814